It is a mad idea. Just how mad depends on where the wedding will be, of course. If the OP means they have taken over a self-catering villa complex in a well-populated area, it won't be as bad as (a) there will be enough cutlery and crockery for 40 (since there are enough beds), (b) there will be kitchens with basic cooking equipment (but spread between several different kitchens meant for producing meals for maybe 6 people max, which will make things complicated) and (c) there will be food shops/markets.
If OTOH the wedding is in the middle of nowhere with no shops nearby and minimal equipment, it's all a complete non-starter.
The only way I could see this working would be if the wedding breakfast were going to consist of something like this:
Fantastic array of good cheese, salami, pâté, other ready-made/ready to eat savoury stuff, lovely flavoursome tomatoes, olives, lots of fruit, lots of delicious bread, good butter/extra virgin olive oil.
Wedding cake bought from UK or ordered from a local place.
Lots and lots of good wine to wash it all down.
Not difficult to get hold of or to lay out on the day, all self-service.
Personally I would love a feast of that kind but it wouldn't necessarily meet everybody's expectations of a wedding breakfast.
Anything that involves actually preparing vegetables, meat, fish, sauces, puddings etc for 40 people is going to take ages and ages, be tiring and messy and stressful, and that's without taking into account the difficulties of, and time taken, getting hold of the stuff in the first place. Then there's the whole question of cooking and finishing the meal - fitting all of that in around the time of the ceremony, serving it up while in wedding finery - the mind boggles.